class Metro {

  constructor(_ms) {

    this.ms = _ms;

    this.timestamp = millis();

  }

  bang(_ms) {

    if ((this.timestamp + this.ms) < millis()) {

      this.timestamp = millis();

      return true;

    }

    return false;

  }

}

​

var metro;

function setup() {

  createCanvas(400, 400);

  metro = new Metro(1000);

}

​

function draw() {

  background(220);

  if (metro.bang()) {

    print("500ms");

  }

}